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We present a new 128-bit block cipher called Camellia. Camellia supports 128-bit block size and 128-, 192-, and 256-bit keys, i.e., the same interface specifications as the Advanced Encryption Standard (AES). Efficiency on both software and hardware platforms is a remarkable characteristic of Camellia in addition to its high level of security. It is confirmed that Camellia provides strong security against differential and linear cryptanalyses. Compared to the AES finalists, i.e., MARS, RC6, Rijndael, Serpent, and Twofish, Camellia offers at least comparable encryption speed in software and hardware. An optimized implementation of Camellia in assembly language can encrypt on a Pentium III (800MHz) at the rate of more than 276 Mbits per second, which is much faster than the speed of an optimized DES implementation. In addition, a distinguishing feature is its small hardware design. The hardware design, which includes encryption and decryption and key schedule, occupies approximately 11K gates, which is the smallest among all existing 128-bit block ciphers as far as we know.

Abstract. We propose a new 128-bit blockcipher CLEFIA supporting key lengths of 128, 192 and 256 bits, which is compatible with AES. CLEFIA achieves enough immunity against known attacks and flexibility for efficient implementation in both hardware and software by adopting several novel and state-of-the-art design techniques. CLEFIA achieves a good performance profile both in hardware and software. In hardware using a 0.09 μm CMOS ASIC library, about 1.60 Gbps with less than 6 Kgates, and in software, about 13 cycles/byte, 1.48 Gbps on 2.4 GHz AMD Athlon 64 is achieved. CLEFIA is a highly efficient blockcipher, especially in hardware.

In this paper we systematically study the differential properties of addition modulo 2 n. We derive Θ(log n)-time algorithms for most of the properties, including differential probability of addition. We also present log-time algorithms for finding good differentials. Despite the apparent simplicity of modular addition, the best known algorithms require naive exhaustive computation. Our results represent a significant improvement over them. In the most extreme case, we present a complexity reduction from Ω(2 4n) to Θ(log n).

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